Telephone-exchange system



S. B. WILLIAMS, JR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG-12,1918.

1,384,125. Patented Man16,1920.

3 SHEETS$HEET I.

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S. B. WILLIAMS, JR.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED AUG. I2, 1918.

Patented Mar. 16, 1920.

3'SHEETSSHEET 2.

S. B. WILLIAMS, JR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG-12,1918- Patented Mar. 16, 1920.

3 SHEETS-SHEET 3.

v uurrnn STATES PATENT OFFICE.

SAMUEL B. WILLIAMS, JR., OF BROQKLYN, NEW YORKQASSIGNGR TO WESTERN I ELECTRIC COMPANY, INGGR-POBATED, O33 YORK, N. "2.. 'A COBYORA'IION OF NEW YORK.

TELEPHGNE-EXCH Specification of Letters Patent.

iren SYSTEM.

Application filed August 12. 1518. Serial No. 249,522.-

To all IU/tO/H. it may concern.

Be it known that I, SAMUEL B. VVILLIAMS, (in, a citizen of the United States, residing Brooklyn in the county of Kings, State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to S\ :tems of the call distributing type in which automatic switches are employed for a selector switch which acts to select an available operators position and find an idle connecting circuit of that position. The telephone lines are arranged in groups, and the lines of each group are multiply conuected with the terminals of a group of finder switches. The finder circuits of each group of finder switches have access through their assoclated selector switches to the con necting circuits of a plurality of operators" positions, the connecting circuits being multipled to banks of contact terminals on the selector switches.

in the system of this invention the lines i are not provided with line and cutoff relays.

instead, the arrangement is such that one or another of the finder switches that serve each group of lines is constantly rotating, with its brushes successively engaging the terminals of all of the lines of the group.

When the terminals of a calling line are engaged, the brushes oi the switch are stopped on the terminals of this line, and another finder switch serving the same group of lines is started and continues in rotation until it finds a calling line, whenit is stopped and starts another finder switch, and so on.

One of the objects of the present inven tion is to provide in connection with such a system as that outlined above an improved finder circuit and associated: apparatus, whereby the frequency with which each line is tested by the hunting finder circuit is increased andv the calling time or the calling subscriber is correspondingly reduced; or whereby, conversely, the number of lines in the line group may be increased without increasing the calling time; whereby the reliability of the system with respect to the response of a testing finder circuit to a calling. line may be increased; whereby each calling line may be insured the sole use of one oi the finder circuits for establishing its connection; and whereby the finder circ'uit may continue to test for an available operators position, without commencing its test for a connecting circuit, until an available position is found.

in accomplishing the objects set forth above, the finder circuit is provided with a plurality of branches, two in the present instance,and the finder switch is provided with a. corresponding plurality of sets of brushes upon which these branches terminate. The finder switch brushes are permit-q uentl y mounted in fixed relation to each othliathe finder circuit branches extending to the finder switch brushes is equipped with test ing apparatus which, when it operates, is llective to control the stopping of the switch and, the starting of another finder switch of the group. The testing apparatus associated with each branch in operating nection or" the finder circuit with that branch and excludes the finder circuit from connection with the other branch.

Inasmuch as the telephone lines served by the finder switch constitute a single group, the result of this arrangement is that also brings about the completion of the conin each complete rotation of the finder connecti the terminals of calling lines at the Consequently for a given speed of rotation of the finder switch, the average time which clapses from the moment a calling subscriber takes his telephone receirer "from its hool:

until connection is completed with the terc calling time. as each line in the gin,

is tested twice in each rotation oi the switch. (Jr with the same calling time and the same ize of line groups the speed of rotation of .he switch may be halt 01 that which it otherwise would be a thing which may be found desirable under certain circumstances;

Furthermore, by providing the finder circuit with two branches both of which are bi", ught successively into operative relation with each line of the entire line group the chance oi the finder circuit tailing to be extended to a calling line is just half of wha it otaerwise would be. it for any reason one of the testing branches fails to respond to the calling condition of a line as the corresponding brushes pass over the line terminals as for inutance through ailure of a brush to engage the cont-at terminals or hiilure of the testing relays of that branch operate. a second tel t is made a moment la h the passing of the brushes associated with the other branch over the terminals or the ceiling line. Thus each 'finc circuit is provided with duplicate testing means, as a consequence oi? which the operation of the system is made more reliable.

The testing devices assoia ed with the two 1) 'anches of the finder circuit are so the conintei'relateo and so conn ctcd with trolling mechanism of the finder switcn, that either device when it operates st n; the brushes of the [in ier switch, and operates finder circuit con oll no mechanism tlai causes the finder :i c to be definitely connected wit 1 the brcich associated with the testing device which. has been actuated, and

to be del iitely excludeiv t'Loin the other 1 L branch until the operator acts to relea e c on. Furthe row, in. relation hip is such that when the b-usl-es or the two branches of the finder circuit both-engage instant. a preference exercised ii if a certain one ot the branches so as to ure ient the possibility of the finder c cuit b connected with two calling lines at t time. ll hen one or the other devices has operated to ton the i i der switch and bring about th' deli; ite conn ction of the finder circrit with t branch both testing devices are from operative relation witl, t cult, and held disconnected inti when the connection is released.

. r e finder circuit selects an availble onerator s position and'extends the circuit o ai idle co meeting cord or that posi- 31, operates first o select the position, and then to find idle connecting circuit. In accordance with one of the features oi the present invention the organization is such that it the selector switch fails to select an operators position, as, for instance, through ility of all of the positions, Ll

lector switch ti rough the medium c a tch is prevented from proceeding; to tluzt stage of its movement wher an idle connectui circuit is selected, but instead caused'to return nnni diately and then re- D o-eat its operator-selecting movement, the snitci continuing to repeat this stage of its movement until one of t e operators positions becomes selectable. In the present embodiment of the invention this is accomplished by providing r hunt controllingmechanism which is made operative to bring about av repetition of the operator-selecting movement of the switch at the conclusion of that stage of the movement, and before the (:01 ne ting circuit selecting stage 01 the iROYQHlGllt is ei tor-d into, and further pro means actuated the successful selection of an operators position for preenting' the rehunt COlltlOlllDg lllQCllZllllSlll F0111 becoming operative. The return and rehunting operation or the selector switch is coinplished through the medium of the finder circuit sequen switch; which is aused to more thro its controlling cycle and back into posit-ion ior starting theopcrater-sole DIOVQIHGD'C of the selector switch; and means are provided whereby the sequence switch is enabled to more through is various controlling; stat es wi hout breakig the connect on oi th. 1 l circuit with to the accompanying draware 1 and are side spectirely partly in or tier switch; and Fig tlier aid placed side bv es extending to diagrammatically organization iding of the in- -inatically a brushes. inals with .1 two lines one to these ier e paratus m 1 m (if; 11 (iCiQ cuit at this position, and the springjack of a i, 20 on which the line terminals associated with the lines at the central oliice; Fig. 3 also shows one finder circuit complete, together with enough of two other finder circuits of the group to indicate the Way the circuits are interconnected; and Fig. e shows a selector switch, one of the connecting circuits at one of the positions to which the selector switch has access, the operators cirline with which connection may be completed by inserting the calling plug of the connecting circuit. I

l: iterring to Fig. 1 and Fig. 2, the line finder switch comprises a stationary drum are mounted, a rotating yoke or pair of arms 92 carrying two sets of brushes for engaging the euposed surfaces of the line terminals on the periphery of the stationary drum, a slipring collector 91 through which the brushes are connected with the external circuit, driving mechanism, and two magnets 80 and 83 for controlling the movement orthe rotating brush carrying yoke. The abovementioned parts are mounted upon the supporting frame 90. The stationary terminals are rranged in sets 56, 57, 58 and 59 which are insulatedly mounted on the drum; and as many of these sets of terminals are n-ovided as may be desiredf As show in the d awings, the drum is equipped with 50 sins oi terminals. T his may be increased to 100 r more sets if desired. ryinpyoke 92 is carried upon the rotatable shati: S9, and each arm carries aset. or brushes 60, (i1, 62, 63 and70, 71, 72., -73, rcspectirely, the sets of brushes beingarranged simultaneously to engage sets of con tact terminals at diametrically opposite points on the stationary drum. The shaft also has mounted. upon it the collector 91 consisting of a hub ot'insulating material slip-rings, one for each of carrying eight the brushes of the two sets. Cooi'ierating with the slip-rings are two sets of brushes o connected by way of. the associated slinrings with the brushes 60, 61, 62 and GS.

and the second mentioned set of brushes beiug connected by way or' the associated slip: 1.

rings with the brushes 70,71, 7 and 73.

The driving ot the brush-carrying yoke is effected by means of a pair of friction dislis 79 and 69, the first of which is secured to the shaft 89 and the second of which is carried upon the constantly rotating power shaft- 68. These two disks are norn'ially out oi? enga- 'ernent VJ hen the motor 80. is energized, the friction disk 79 wnic is resiliently connected with the driven shaft is magnetically attracted and brought into engagement with the edge of the constantly 7 9 and the shaft 89 to which it is attached The brush earone he each sct o controlling lever 27 cit-each set of brushes is rotating. friction disk 69. The disk are thus caused to rotate as long as the motor magnet 80 is energized. When current ceases to iiow through the motor magnet 80, the disk 79 is retrarted and the rotation of the shaft 89 with its brush-carrying arms is stopped. To insure the instant stopping of the shaft 89 with its associated parts, a holding magnet 83 is provided for moving a pawl 84 into engagement with the. ratchet cess. Each of the switches comprises a ou.

tical shaft 37 carrying as many sets 26 of line brushes as there are banks of contact terminals in the panel board. The brushes 18,19, 20 and 21 of each set arenormally held apart by bi" controlling lever 27, so that the brushes a e kept out of engagement with the stationary terminals as the brushes are moved up. The upward moven'eentoi the sets oi? brushes is effected by the energization of the lip-drive magnet 34-, which b1: an extension of the bmslrcarrvi g rod 37 into engagementwith a conl rotating driving member and the downward movement of the brushes is brought out by the energization of the (lOWll-{illYQ magnet which moves the. extension of the brush-carrying rod 37 into engagementwith a member 35 which is constantly rotatin in the reverse direction.

The tripping of a particular set of brushes :26 for engagement with the stationary terminals of -119 associated contact bank 7 of' the trip e of tripping fingers i rushes.

is eli ccted by means which ca ries with. t e

. ted tripping linger 28. the nor not the trippingind 30 2-8 are out of thepath d movement of. the tripping elevacorresponding inger 28 is swung into engage ment with the associated lug 29, so that continued. upward movement of the brush set willcause the tilting oi the brush con trolling lever "27 of. this particular set of ing rod 30' The brush.

each. degree of the upward.

at the -ino veprovided with a .rearwardly extending tripping lug it rich is adapted to cooperate a. tripping lug when the rotation of the rod occurs remains in engagement with the lug. while the other fingers swing beyond the line of upward movement of their associated lugs.

The rotation of the tripping rod 3%) effected by the tripping magnet under the control. of brush t8 and contact bank 50 at the top of the brush-carrying rod 37. The contact bank 50 is so positioned that in the u award movement of the bruslrcarrvin K 1 rod the brush l8 engages the first ot the terminals 50 when the tripping lug 29 ot the lowest set of brushes is opposite the corresponding tripping finger 28, so that the second of the terminals 50 is engaged when the tripping lug 29 of the second set of brushes from the bottom is opposite its corresponding tripping finger and so on, the last of the terminals 50 being engaged by the brush 1-8 when the tripping lug 29 of the highest set of brushes on the shatt is opposite its associated tripping finger. The arrangement is also such that the brush t8 has reached the highest of the contacts 50 of the associated bank before the brush sets 26 reach the lowest sets of terminals ot their associated banks. Thus the selection of a particular set of brushes for engagement with its contact bank is completed before the contact banks are reached in the upward movementof the switch.

At the top of the brush-carrying rod 3'? there is an arm carrying a contact brush which, in the upward movement of switch, is moved over a commutator 51 and successively engages the segments Y, H and X. The segment Y is engaged when the lnush-carrying rod 37 is at the limit of its downward movement; the segment H is engaged as the brush 48 passes beyond the highest of the contacts 50 and'botore the brush sets 26 engage their respective contact banks; and the segment X is engaged when the brush-carrvin rod '3'? reaches the v C! hunt of 1ts upward movement.

Certaln of the circuits of the system controlled by sequence switches which designated 100, 200 and $00. These sequence switches may be of the type disclosed in Patent 1,127,808, issued February 9, 1915, to Reynolds & Baldwin. Each consists a electro-magnetically controlled motor or driving mechanism and a number of associated switch cams. The switch cams associated with the sequence switch 100 are designated. 101 to 103. inclusive; those associated with each of the sequent switches 200 aredesignated 01 to 235, inclusiw; and those associated with each of the sequcnce switches lOO are designated i i-O1 to 4:12, inclusive. To each or the contacts associated with the various sequence switch cams are applied certain numerals. These numerals in the case of the cams 101, 201 and 401 indicate the only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all of the other co acts oi each sequence switch indicate the only positions of the particular sequence switch in which the associated contacts are closed These positions of the various sequence tches, and the stages of operation with which these positions are associated. are as follows:

Operators sequenceswitch 100.

1 Normal.

Unlock.

Fimlc 1 Normal.

2 Hunting calling line.

6 Awaiting relay.

4 Hunting idle operator.

9 Hunting idle connecting circuit.

Talking.

Switch returning.

sequence switch 900.

listening 7907 8097mm: switch, {10/ 1 Normal. 6 Llstenlng in. 8 Listening out.

In detail .the operation ot the system oi this invention is as follows:

quence switch contact back contact i of relays", sequence switch contact (2), sequence switch contact 23-i- (2). back contact of relay t1 and back contact and inner left-hand armature 0i relay 4-2 to ground. The flow current in this circuit keeps the motor magnet energized and the driving disk 69 and the driven disk 7:1 ot the finder switch in engagement.

It will further be assumed that the subscriber at station A takes his telephone rcceirer from its hook, and that the set o't brushes 60, 61, 62, 63 is the first of the two sets to engage the terminals 56, 57, 58, 59 as sociated with the line extending to station A. hen the brushes engage the line teruses- 125 ininals, a circuit is closed which extends from battery by way of finder sequence switch contact 226 (2), winding of relay 45, finder sequence switch contact 229 (2), conductor 11, brush 66 and associated slip-ring oi the finder switch LE, finder brush 62 and tern'iinal 58 or" the calling line, conductor resistance 6 to ground. The operation of relay a5 resulting from the closure of this circuit closes a circuit that extends from battery by way of finder sequence switch contact 222 (2), le1fi-hand winding of relay 4:0, finder sequence switch contact 221 (2), inner armature and front contact of relay 4:5, finder sequence switch contact 228 (2) conductor 10, through the finder switch to terminal 57 and associated conductor 2 of the calling line, thence through the substation switch and back over limb 1 of the calling line to terminal of the finder switch through the finder switch to conductor 9 of the finder circuit, finder sequence switch con-- tact 227 (2), outer front contact and armature of relay 4:5, finder sequence switch con tact 220 (2) and righthand winding of relay 4-0 to ground. As a result ofthe closure of this circuit the relay L0 is energized and closes a circuit that extends from battery in parallel. branches through the winding of the finder sequence switch motor magnet 200 and the line finder switch holding magnet 83, finder sequence switch contact 225 (2), front contact and armature of relay L0, finder sequence switch contact 228 (2), finder sequence switch contact 234 (2), back contact and armature of relay a1 and back contact and inner left-hand armature or relay 42 to ground. Art the same time the energization of the relay 40 opens at its back contact and armature thepreviously traced circuit over which current heretofore has lowed for energizing the motor magnet oi the line finder switch. The line finder switch consequently is stopped with its brushes 60 61, 02. 63 on the terminals of the calling line the stopping beino made positive by the energiaation of the under switch holding mac,- net and the finder sequence switch 200 is energized to cause the movement of the sermencc switch out of position 2 in which it has been resting.

It may be explained at this point that the inder switch is not stopped by the passage of its brushes over the terminals of lines which ha V0 already been connected with, for the reason that establishing connection with the closes a low resistance path from battery to the test conductor o't'sueh line, either by way of. resistance 93 of the finder circuit or re 13 o"? the connecting cord, through which the connection is established it the line is a calling line. or by way of relay 338 associated with the calling plug 334.- if. the line is a called line; which low resistance path shunts out and prevents the operation of the relay 4:5 or the finder circuit of the hunting finder switch. so that this relay does not operate to bring its associated relay it) into connection with the terminals of such a line.

Of the line finder switches Ll? serving the L OUP of telephone lines only one is in opition at a time. The other line finder switches of the group either have be n appropriated by other calling lines and are in use extending the connections of such lines, or are waiting with their sequence switches 200 in position 1. As soon as the finder switch Ll finds and stops ugonthe terminals ot' the calling line and causes the movement of the associated sequence switch 200 out 0t position 2 as described abov the se quencc switch of another of the group, of finder circuits is moved out 0 its normal position 1 and into its hunting position and causes the associated finder switch to start rotating. This is accomplished by means of a circuit which is closed from battery way of the sequence switch motor magnet 200 of the waiting finder circuit, assuming that this is finder circuit F, outer letl't finder circuit F to move to position 2 and close the energizing circuitci' thounetor magnet 80 of the associated finder switch to start the rotation of that switch; it the finder circuit F is assumed to be busy and the? fore to have its sequence switch in some position between 6 and 18. at the time the tinder switch of finder circuit F seizes the calling line, and at this time the finder cirunit F is idle and has its sequence switch 200 in position 1 then the circuit would be l'ro a battery through motor magnet 200 back contact of relay e2 and contact 202 V l) oi? finder clrcuit F sequence switch contact 202 (6 to 18) of finder circuiti outer right-hand armature and back contact of re lay 42 of finder circuit F, and to ground by way otiisequcnce switch contact 203 (3to 5) oil that tinder circuit. Thus the fir t in order or": the finder circuits w h is idly-Wis selected and its finder switch s,

rrtcd in rotation upon the seizure o? a calling line by the finder switch which has been hunting.

If, under heavy trafiic conditlons, all of the other finder circuits are in use when the uniting finder switch seizes a calling line,

none of them is in condition to have its sequence switch. 200 moved into position 2 to take up the hunt when the hunting switch is stopped and moves its sequence switch out of position 2. To take care of this situation a lillO series path to ground is closed by way of the sequence switch contacts 20a (6 to l) of all of the finder circuits, which path is read to act immediately upon the return of any of the finder sequence switches to normal to move that switch out of position 1, and into position 2 where the rotation of the associated linder switch is started. This ath to ground by way of the cams 201 of all ot' the finder circuit sequence switches in series, also operates to more into position 2 the sequence switch of one oi the finder circuits when all of the sequence switches for any reason are standing in their normal or 1 position.

In the operation of the system, as thus far described, the finder circuit F has seized the calling line of station A. and the brushes $0, 61, 62, 63 of the finder switch are resting upon the calling line terminals. the sequence switch {200 ct finder circuit F has moved out of position 2, and the sequence switch of finder circuit F has moved from position 1 to position and has caused the associates'l linder switch to take up the hunt for calling lines. Upon leaving position 2 the sequence switch 200 of finder circuit F continues to move until it reaches and comes to rest in position (3. In position 6 a circuit is closed that extends from battery to finder sequence switch contact (6), winding of relay in and finder sequence switch contact 216 (6) to ground. When. as a result, the rela l5 attracts its armatures, it closes a locking circuit for itself that extends by way of finder sequence switch Contact 218 (6 to 7), inner front contact and armature oi relay l5, finder sequence switch contact 221 to 8), sequence s itch contact 208 ((3 to S), and brush i8 and normal resting contact -19 of the selector switch CS to ground.

\Vhen relay has thus lreen locked up the operation of testing for an idleoperators position is in rent iness to he proceeded with.

and a circuit closed by the relay 45 for moving the finder sequence switch from its waiting position (3 to in 4 perator-testing position 7. This circuit extends from batter} by way of the motor i'nagneti200 and contact ((3) of the finder sequence switch. outer front contact and armature of relay 4.5., and sequence switch contact 220 (6 to to ground. In position 7 of the finder sequence switch a circuitclosed that extenos from battery by way of the rip-drive magnet 34; of the selector switch CS. sequence switch contact 215 (7), outer front contact and armature of relay %5 and sequence switch contact 220 (6 to to ground. As the brusharrying rod 37 of the selector switch moves up, the .operators test brush 4L8 successively engages the contact terminals 5-0 associated with the test wires of the various operators" positions to which the selector switch has access: and at the instant of engagement of the brush 4:8

with ach contact terminal 50 the tripping lug 29 of the set of brushes 26 having access to the connecting circuits of the correspond ing operators position has reached a posi tion where it is opposite the associated tripping finger 28. As will hereinafter be described, the test wire 82 of each operators position that is busy or otherwise unavailable is grounded. The normal resting contact as for the brush as is also grounded; and as the test brush i8 is so related to, its ass ciated contact terminals that it makes contact with one before breaking with the other, the previously traced circuit controlled by the testv brush as and including the winding of relay a5 continues closed until the test. brush reaches the terminal 50 of an operators position that is available and therefore has its test wF'e S2. ogen. When this occurs the relay is deenergized, and in releasing its armatures, opens at its outer front contact and armature the previously' traced energizing circuit of the up -drivo magnet 3i. It also closes a circuit that extends from battery through the motor magnet and contact 217 (7) of the finder sequence switch, outer back contact and armature of relay to, and sequence switch contact 220 (6 to 9) to ground. The closure of this circuit causes the finder sequence switch 200 to. more from position 7 to position 9.

As the finder sequence switch 200 reaches position 8 a circuit is closed that extends from battery through the winding of the trip magnet 32 of the selector switch CS and sequence switch contact 209 (8. to 9) to ground. Theselecter switch CS is at this moment at. rest, the energizing circuit of the up-drive magnet 34: having been broken upon the finding of an available operators position as described. In the present instance it is assinned that the operators position corresponding with the lowest terminal 0' the test bank 50 was available, and that therefore the elevator of the selector switch moves upward. just far enough to bring the tripping lug 29 of the lowest set of brushes opposite the associatel tripping finger 28.

herefore the energiraation of the tripping magnet 32 as sequence switch 200 reaches position 8 turns the tripping rod and brings the tripping finger associated with the lowest set of brushes 18, 19. 20, 21 into engagemcntwith the corresponding tripping lug 29. The rotation of the tripping rod 30 swings all of the other tripping fingers 2S far enough to clear their associated trip ping lugs when the upward movement of the brush-carrying rod 37 is resumed. Ininiediately after the tripping members of the selected set of brushes are brought into engagement a circuitis closed that extends in in battery through the lip-drive magnet- 34. finder sequence switch contact 217 (9). outer back contact and armature of relay operatofis sequence and sequence switch contact 220 (6 to 9) to ground. This causes the brushes of the selector switch to resume their upward movement, the brushes of the set whose tripping lug is in engagement with the tripping fin- .28 being tripped and made active, and the brushes of the other sets being held apart to clear the terminals ot the associated contact ban 5.

The selected set of brushes oi the selector switch CS now caused to move over the terminals of the associated contact hank until .it finds and is brought to rest upon the terminals of: an idle connecting circuit. Before describing this, however, it will be well to consider certain of the operations which in the meanwhile are occurring in the operators circuits of the selected position. Referring to Fig. 1, when the operator is not at her position the telephone plug is witlnlrawn from the spring jack 195, and the t conductor 82 is connected to groinid h of the switch spring 197 and. resting contact of the spring jack 1%. JV hen the operator is at her position, the presence of the telephone plug in the spring jack connects the test conductor 8:2 by way of the switch spring 197 and its alternate contact with battery by way of the winding of the relay hi8. il hen thus connected, no current flows through the conductor 89. when the test brush 48 of the selector switch, which is also connected with battery by way on? the test iv t5, engages the corresponding test contact 50. But as soon as the relay of the finder circuit releases its armaturcs as a result oi. the interruption oi current flow through its circuit, when the test contact 50 connected with battery by way of the winding of relay 148 is engaged, it completes a circuit that extends from battery by way oi the winding of relay 1&8 (see Fig. 4-), alternate contact and switch sprin 19'? oi? the operators telephone spring jack, conductor 82, test Contact 50 a?- d test crush 4:8 01' the selector .witch, tinder sequence switch contact 908 (6 to 8), sequence switch contact (6 to 8), inner armature a; 1 back contact of relay %5, and sequence switch contact 216 7 to 8) to ground. Relay 14:8 in operating closes a locking circuit for itse f that extends by t its right-hand i'ront coi'itact and t): iture and contact 103 (1 to 17) of the itch to ground. Relay 14:8 in operating also closes a circuit that on .ends from battery through the motor magnet and contact 102 (1) of the op erators sequence switch, and the le'tt-hand trout contact and armature. of relay 148 to ground. The operatmrs sequence switch thereupon moves out of position 1 and continuos to rotate until reaches and comes to rest in. position 18. The locking ground which therelay 14-8 in operating applies at its right-hand front contact and armature establishes a grounded condition of the test wire 82 which prevents the selection or" this operators position by any other selector switch; and also provides a circuit for energizing the relay 156 by way of the back contact of relay 157. Relay 156 in operating closes at its front contact and armature a circuit for the illumination 01? the pilot lamp 167, which notifies the operator that her position has been selected by an incoming call. This locking ground by way of cam 103 of the operators sequence switch is maintained until just before the operators sequence switch reaches and comes to rest in posit-ion 18. The speed of rotation of the sequence switch 100 is such that bctore the locking ground. is removed by the passin oi the sequence switch beyond position 11 another ground is applied to the system of circuits in question by way of conductor and contact 111 (2 to 6) of the listening keysequence svitch, as will hereinafter be described.

Returnin now to the finding of an idle connecting circuit, the selected set of brushes of the selector switch CS moves up it successively comes into engagement with the terminals associated with connecting circuits of the selected operators position. When the connecting circuit is in use, its terminal 25 on the selector switch is connected with battery by way of the righthand armature and front contact of the con necting circuit relay 95 and one or the other sequence switch cam 108, the relay 95 being energized as long as theconnecting circuit is in use But when the test brush. 21 of the selected set of brushes engages the coin tact terminal 25 or a connecting circuit that is not in use, a, circuit is completed that extends, from battery byway of finder sequence switch contact 22 {6 to 9), the wind of relay 4E5, tinder sequence switch contact 210 (9), conductor 55, brush 21 and contact terminal 25 of the selector switch, connecting circuit conductor 88, resting contact and switch spring 161. of disconnect key 180, and right-hand armature and back contact of relay 95 to ground. Relay l5 in operating opens at its outer back contact and armature the energizing circuit of the rip-drive magnet 34, thus stopping the up ward movement of the selector switch In the movement of the finder sequence switch from position. 9 to position 17, a circuit is closed that extends from battery through the motor magnet and contact 110 (1) or the listening key sequence switch LOO (see Fig-1), left-hand armature and back contact of relay 95. left-hand back contact and armature of relay 13. back contact and switch spring of relay 81, conductor 87, contact terminal brush 20 of the selector itch CS. con .ctor 5+1. and finder sequence switch contact 212 (11 to 16) to ground. As a ot the closure of this circuit hkey sequence switch 400 is nioveo 1 n i s norn'ial position 1 to its listening-i position 6. i l hen the sequence switch 1-60 caches position 2 a 1 circuit is closed that esten ls from battery through tic winding r sequence switch contact 112 {2 to 6), and thence by way of back contact and switch. Spring of relay 81 to ground at finder sequence switch contact 212 (11 to 16) over the path already traced. When relay 13 operates it closes at its left-hand front contact and i'nature a locking path for itself in shunt 05" its initial energizing path by way 0% sequence switch contact 1-12 (2 to 6). ll hen the tinder se quence switch passes through position 16 and comes to rest in positimi 17. the energizing path to ground :tor the relay 18 by way of finder sequence switch contact 212- (11 to 16) is replaced by a path to ground that ex.- tcnds by way of finder sequence switch contact 212 (16 to 17), inner lo yer armature and back contact of relay at. finder sequence switch cont-act (3 to 17). conductor 11 and thence through the line finder-switch LF to conductor '7 associated with the calling line. and to ground by way of the resistance coil 6. This circuit is maintained as a holding circuit until the operator acts to release the connection.

lVhen relay 13 operates upon the selection of the connecting circuit. it closes a circuit that extends in parallel branches "from battery through the lamps 329 and (see Fig. 1), conductor 255 and lower front contact and right-hand armature of relay 13 to ground. The closure of this circuit causes the illui'nination of lamp 329 to indicate to the operator the particular connecting ciron it to which the call. of whicl'i she has been notified by the lighting; of her pilot lamp 167, is being extended. The lamp 335, however, is not lighted, as it shunted out by the answering I 331, the circuit of which lled at the calling subscribers switchhook in the usual way. Relay 13 in operating also closes a circuit that extends from battery throng the winding of relay 95 and to ground by way of the upper front contact and right hand arrnature of relay 13. 95 in operating disconnects, at its righthand armature. the

contact 411 to 6) to the operators conductor 82 and t0 the energizing circuit test conductor 88 from ground and connects 'th battery by way of listening key se- (8 to 5) and reto S car-n lOS switch completes S8 to battery by "i tor 252 and r "stance coil 159, so that the test conductor is connected with battery by way of one or the other oi these qua-ice switch contact- 108 nce coil 1 8. In positi 0-. the connecting sequence test conductor paths s long as the relay )5- is energized.

' W am. the listening key sequence switch 4200 nnnrcs to listening-in position 6 as the result oi the selection of the connecting circuit as has been described. it breaks at its cams 4e03, d0 1, 105 and 106 the normal connection of the talking conductors S5 and 86 with the conductors and 25-h rcspectively, and connects these conductors in a loop including conductors 2-36, 237, 238 and 239 through which connection is had with. the operators telephone set and conunon position apparatus. The operators telephone set, which is organized in the usual way, is connected with this loop by way of the conductors 2414c and The loop includes the ringback key 18 1-, by means of which the operator is enabled to connect current from the generator 199 back over the circuit for ringing the calling subscribe-us bell. in moving to its listening-in position 6 the listening key sequence switch also applies ground by way of conductor 2 1-1 and including the windings of the relays 148 and 156 of the operators position. As has been described, this path to ground is closed in the normal operation or the system before the timing sequence switch 100 has passed beyond position 17 so that the operators position is held continuously unselectable. and the relays 148 and 156 are kept energized from the n'iornent the position is first selected. When the listening key sequence switch reaches position 6 it closes a circuit that extends from battery through the winding of relay 157 (see Fig. 4.), con ductor 251, sequence switch contact 407 (6) to ground. Relay 157 in operating opens the energizing circuit of relay 156 and releases that relay, thus extinguishing the pilot lamp 167.

The operator may now communicate with the callingsubscriber, the talking circuit connected with a telephone line in the same manner in which the spring jacks 3 and 3 (see Fig. are connected with the lines 01" stations A and A and their associated apparatus. If the line is busy the presence of potential upon the sleeve of the spring jack 339 results in a flow of current which acts inductively through the wind ings of the repeatingcoil 333 and produces a click in the operator s telephone receiver in a manner Well understood in the art. If the called line is free, the insertion of the calling plug 33a closes a circuit that extends vfrom battery through the Winding of relay 338, registering sleeve contacts of the calling plug and called line sprin jack 339, and to ground by ay of the resistance 340. Relay 338 in operating closes a circult that extends from battery through the calling supervisory lamp 336 and inner front contact and armature of relay 338 to ground. At the same time the energizing circuit of the calling lamp 329 is broken at the outerback contact and armature of relay 338 and that lamp is extin uished. The operator signals the called subscriberbv applying ringing current from the genorator. 199 by means of the ringing key 330 in the usual Way. When the called subscriber responds, the calling supervisory relay 332 is energized and extinguishes the calling supervisory lamp .336 by completing a shunt about it.

The operatormay noiv disconnect her telephone setfrom the connecting circuit, which she does bypressing the listening out key 187 (see Fig. a). The pressing of this key closes a circuit that extends from bat-- tery through the motor magnet and Oiltact 409 (2 to 6) of the listening hey sequence switch 400, condutor 247 and contacts of the listening-out key 187 to ground. This causes the listenin hey sequence switch to move out of its listening-in posi} tion 6 to come to rest in its listening out position 8, in Which position. the cams 403, 1:04:,405 and 40s of the listening key sequence switch act to disconnect the operators loop conductors 236, 237, 238 and from the connecting circuit, and to connect the connecting conductors 86, and 254 directly together for talking purposes. W hen the listening key sequence switch moves to position 8, as the result Gill pressing the listening-out key 18?, the path to ground by Way of listening hey seque e contact 411 (2 to 6) isopened, thus olearing operators position test conductor and rendering the position selectable. The interruption of the path togii'ound also deenergizes relay 1 18; and thatrelay in leasingcloses a circuit that extends from battery through the motor magnet and contact 102 (18) of the operators sequence switch 100 to ground by Way of the left hand back contact and armature of relay M8. The operators sequence switch thereupon returns to its normal or 1 position, and is in condition to respond, in the manner already described, to another selection oi the operators POSltlOll. The movement ofthe listening hey sequence switch out of position 6 also, opens, at sequence switch contact e07 (6),"the energizing circuit of the relay157, and that relay in releasing again places relay 156 in readiness to display tie pilot lamp 167 upon the selection of the position.

It at any time the operator should have occasion to supervise the connection, she may again bring her telephone into connection with theconnecting circuit by pressing the listening-in key 183 (see Fig. 4). This closes a circuit that extends from battery through the motor magnet and contact 409 (8) of the listening hey sequence switch, contacts oi listening-in key 183, conductor 2&9 and back contact and armature of relay 156to ground. The listening key sequence switch thereupon moves out of the listening-out position 8, through normal position 1. and into listening-in position 6, being caused to continue to move through position 1 by means of a circuit completed for the motor magnet by Way of listening key sequence contact 4-10 (1)," left-handarn1ature and front contact of relay 95, and upper front contact and right-hand armature of relay 13 to ground. ll" it should happen that the operators position has just been se lected by an incoming call at the moment that the operator presses the listening-in key 383, the encrgization of the relay'156 that results from the selection of the position opens the path to ground at the back contactand armature of relay 156, and thus prevents the closure of the listening-in circuit. In this way the operator is prevented from bringing her telephone into connnuni-' tion With an existing connection when it just aboutto be connected with another 0011- necting circuit as the result of incoming call.

l i hen the subscribers hang up their telephone receivers at the end ofthe conversation, the consequent deenergization of the cord circuit supervisory relays 331 and car a the lighting of the corresponding supe sory lamps 335' and 336. If, before releas the connection, or at any time during the existence of the connection, the operator Wishes'to identify the callins'line fo the purpose oi making a charge iOi' the service, she may doso by operating the line identifying key 165 (see Fig. l),it being assumed that tl e listening key sequence switch is at the time in its listening-inposition 6. hen the key 165 is pressed a circuit is closed that extends from battery through resistance coil 166, contacts of the line identifying key 165, conductor 252, listening key vsequence switch contact 408 (5 to 8), right-hand front contact and armature of relay 95, contacts 161 of disconnect key 160, conductor 88, terminal 25 and brush 21 of the selector switch CS, finder sequence switch contact 210 (17), outer lower armature and back contact of relay a l, conductor 12, through the line finder switch to conductor Sassociated with the calling line, and thence to ground by wa of the lain-p & mounted on the line lamp board 5. This line lamp board is located within view of all the operators and has a lamp for each of the lines, the arrangement of the lamps being in accordance with the iuimerical def ations of the lines, so that any operator, by making and breaking the contacts of her key 165, and noting the po sition on the board 5 of the lamp which is flashing, may identify the line connected with the connecting circuit to which her position apparatus is extended. The resistances 158 and 159, one or the other of which connected in circuit with the lainp as long as the calling line is extended to the connecting circuit, are of relatively high resistance; and the resistance coil 166 associated with the line identifying kc" 165 is of relatively low resistance. The current flow through the line lamp board is therefore normally insutficient to cause the illumination of the lane), the lamp being lighted only when the high nice 15'.) is shunted by the low resistance 166.

\Vhen the operator is informed by the lighting of the cord circuit supervisory lamps and 336 that the subscribers have finished their conversation, she may release the connection by pressing the disconnect key 160. This closes, at contacts 163 of the key 160, a circuit for energizing the relay S1; and that relay in operating opens the previously traced circuit over which up to tl is time the relay 13 has been held energized. Relay 13 in releasing closes, by way of its right-hand armature and back contact and listening key sequence switch cont-a t 410 (6 and 8), a circuit for energizing the motor magnet of the listening key sequence switch and causing that sw tch to return to its normal or 1 position,-the relay having been released by the opening of its energizing circuit at the upper right-hand front contact and armature of relay 13.

During the continuance of the connection the relay %0 of the finder circuithas acted as a holding relay, the energizing circuit for this relay extending from battery by way of one or the other of the resistance coil branches completed at 0am 408 of the listening key sequence switch, front contact and right-hand armature of relay 95, normally closed contacts 161 of the disconnect key 160, conductor 88', contact terminal and brush 21 of the selector switch CS, conductor 55, finder sequence switch contact 222 (17), left-hand winding of relay 40, finder sequence switch v and right-hand winding ,of relay d0 to ground. This holding; circuit is opened both directly by the opening of the contacts 161 of ke 160 and indirectly by the release of relay 95. The holding relay d0 of the finder circuit therefore becomes inert and in releasing its armature closes a circuit that extends from battery through the motor magnet and contact 22% (17) of the finder sequence switch, back contact and armature of relay -10, finder sequence switch contact 223 (17), and inner back contact and right-hand armature of relay 42 to ground. This causes the finder sequence switch to move from position 17 to position 18. In position 18 a circuit is closed that extends from battery through the downdrive magnet 2-33 of the selector switch and finder sequence switch contact 209 (18) to ground. V hen the selector swit 'h C3 reaches its normal position as the res: of the closureof this circuit, a circuit is c that extends from battery throuil'h then-i: r magnet and con w 206 18) ofthe finder sequence switch, and to ground by way of segment Y and the associated brush of the selector switch con mutator. The closure of this circuit causes the finder sequence switch to more from position 18 to position 1, in which position it remains until its turn cor-res to be moved to position 2, where its associated line finder switch LF takes up the hunt for calling lines, as has already been described. The brushes of the line finder switch remain on the terminals of the line with which the connection had been established; but in position 1 of the finder sequence switch the brushes of one branch are disconnected at the finder sequence switch cams 227, 228, 229 and 210, and the brushes of the other branch are disconnected the finder sequence switch cam, 1 and the outer lower front contact of 1 Al H Upon pressing the disconnect key 160 .1 operator also removes the calling plug 33%- from the spring jack of the called subscribers line, so that the circuits are all rcstored to their normal condition.

As-has been observed, each finder circuit has two testing branches, one branch extend ing to the set of brushes 60, 61, 63 and the other branch Xtending to the set of brushes 70, 71, 72, 73. Each of the nanches is equipped with independently responsive testingappliances and as each of the two sets of brushes engages each of the sets of line terminals of the entire group in each rotation. of the finder switch, every calling line has two chances in each rotation of the finder switch to appropriate the hunting contact 219 (1.

through, and over the conductors 9 and 10.

or 14 and 15, as the case may be, and the associated brushes of the line finder switch to the circuit of the calling line. The relay 41 therefore is under the control of the telephone switchhook at the calling subscribers station. If the calling subscriber hangs up at any time when the finder sequence switch is at a stage of its movement intermediate of its hunting stage 2 and its talking stage 17, the relayjll is deenergized and a circuit is closed that extends from battery through the motor magnet and contact 23% (3 to 16) of the finder sequence switch, back contact and armature of relay etl, and inner left hand back contact and armature of relay 42 to ground. Consequei itly the finder sequence switch noves from the intermediate stage in which it happens to be through position 16 and into position 17. In position 17 a circuit is closed for energizing the motor magnet of the finder sequence switch by way of sequence switch contact 22% (17),

back contact and armature of relay 40, sequence switch contact 223 (17), andinner left-hand back contact and armature of re lay to ground. This moves the finder sequence switch into position 18, in which po sition a circuit is closed for energizing the sequence switch motor magnet by way of sequence switch contact 206, (18), and the Y segment and brush of the selector switch commutator to ground. This moves the finder sequence switch out of position 18 and into its normal or 1 position.

The foregoing is under the assumption that calling subscriber hangs up before the selector switch has completed its selection of the connecting circuit and the finder sequence switch has moved out of position 9. If these acts haveoccurred and the calling line is extended to the connecting circuit at: the time, when the calling subscriber hangs up, then the finder sequence switch is moved to and rests in its talking position 17 until the operator has pressed the disconnecting key 160 in response to the lighting of the calling subscribers lamp 335, which results from the calling subscriber hanging up, when. the movement of the finder sequence switch out of position 17 and the return of the selector switch are effected in the manner hereinbefore described.

In the system of this invention provision is made for automatically continuing the test for an idle operators position in case all of the positions are busy or otherwise unavailable when first tested by the selector switch. It will be remembered that the first stage of the upward movement of the selector switch is for the purpose of testing wire leading to an available position. If

no position is available at the time the test is made, the upward movement of the selector switch elevator continues until the test brush 4:8 has passed over all of the test terininals 50, at which time a grounded brush engages the segment H of the selector switch coin urtator When this occurs a cir cuit is closed that extends from battery in parallel branches through the windings of the relays 42 and 47, finder sequence switch Contact 207 (7), and selector switch commutator H and its corresponding brush to ground. Relay in operating closes a looking circuit for itself and relay 47 by way fits inner right-hand front contact and armature, and finder sequence switch con tact 203 (7 to 5) to ground. Atits lefthand inner front contact and armature relay 1-2 closes a path, by way of finder sequence switch contact 205 (7 to 17), for energizing the finder sequence switch motor magnet. As a result the finder sequence switch moves out of position 7 interrupting at finder sequence switch contact 215 (7 the energizing circuit of the updrive magnet 8%,

which energizing circuit an instant before this has also been interrupted at the outer front contact and armature of relay 45 by the release of that relay as its locking circuit is broken by the passing of the test brush d8 beyond the last of the unavailable,

and therefore grounded, operators position test terminals 50.

When the finder sequence switch moves from position 7, as described, it continues to move until its energizing circuit, closed by the locking up of relay i2, is opened at finder sequence switch contact 205 (7 to 17). The finder sequence switch therefore comes to rest in position 18. In this position, as

has already been described, the circuit of the down-drive magnet 33 is closed at finder sequence switch contact 209 (18) and when the selector switch reaches normal as the re sult of the closure of this circuit the finder the result of the closure of its circuit at sequence switchcontact 206 (218) and the Y segment of the selector switch commutator. In position 1 the circuit of the finder sequence switch motor magnet is again closed by way of the sequence switch contact 205 (1 to 3) and the inner front contact and armature of relay 42, which relay is still locked up by way of its inner right-hand front contact and armature and sequence switch contact 203 (7 to 5 The finder sequence switch therefore is moved through position 3, and continues to move under the control of its cam 201 until it reaches and comes to rest in position 6. In position 6 the test relay to is locked up, the finder sequence switch is moved to position 7, and the selector switch elevator is again moved up to repeat the test for an available operators position, in the manner which has already been described.

it will be noted that when the relay -12 is operated locked up to bring about the rehunt for an available operatcrs position, disconnects ground from the conductor which extends to the back contact of its inner left-hand armature. This is for the purpose of preventing the passage 01 the finder sequence switch through position 2, as it reestablishes the operators hunting condition, from bringing about any change in the circuits already established. For 111- stance, if it is assumed thatthe finder circuit is connected with the calling line by way of the set of brushes 60, 61, 62 and 63, the relay 44 under these conditions being inert, and that the line with the terminals of which the brushes 70, 71 72 and 73 are in engagement is now'calling and has not yet been connected with by another finder switch, then as the finder sequence switch iasses through position 2 in reestablishing the operators hunting condition the relay e1 associated with the brushes 70, 71, 72 and 73 is operated. If it were not for the disconnection of the ground at the inner lei't-handback contact and armature of relay 12, the operation of relay 41 would close the circuit extending from battery in parallel branches through the motor magnet of the finder sequence switch and the holding magnet 83 of the finder switch, finder sequence switch contact 235 (2), left-hand winding of relay 13, finder sequence switch contact 233 (2), front contact and armature of relay s1, and thence to ground at relay 42. The resultant operation of relay 43 would cause that relay to lock up and also close, at its outer front contact and armature, the energizing circuit for the relay Ii 1;. This would interrupt, at the contacts of relay id, the connection assumed to exist between the finder circuit and the calling line by way of the brushes 60, 61 62 and 62 of the finder switch, and would switch the finder circuit tothe other calling line with the terminals of which the brushes 70, 71, 72 and 73 are now assumed to be in engagement. Such action is prevented by the interruption or the ground path at the in nor left-hand back contact and armature of relay d2 when that relay is operated.

' This interruption of the path to ground at the inner left-hand back contact and armature of relay 42 also prevents the motor magnet of the finder switch from being energized to move the finder switch brushes off of the calling line terminals when both test O and 41 are denergized and their is r dacted while the finder sequence switch is passing through position 2 in the rehunt operation.

. The relay 42 is also arranged to control the advance starter wire circuit so as to prevent any interference with the functions of this circuit as the finder sequence switch moves through its cycle in reestablishing the operators hunting condition. When the relay 1'2 operates it opens at its outer left hand back contact and armature the path extending from the motor magnet of the finder sequence switch to finder sequence switch contact 202 (1). This is toprevent the ground applied at the finder sequence switch cam 201 as the sequence switch moves into and out of position 1 from being connnunicated by way of the 202 cam series to the motor magnet of some other finder sequence switch that is standing in position 1 to move that sequence switch into position 2, thus causing the associated finder switch also to start hunting for calling lines. At its outer right-hand armature and back contact, the relay e2 opens the path extending from the 202 cam series to ground by way of contact 203 (3 to 5) of the finder sequence switch that is repeating its cycle, in order to prevent the application of ground to that series to move some other finder sequence switch from its normal position 1 to its hunting position 2. At its right-hand armature and front contact the relay 4:2 closes a shortcircuit of contact 202 (6 to 18) of the associated finder sequence switch in order to prevent the finder sequence switch of the rehunting finder circuit from opening, it passes from position 18 to position 6, the path over which ground is being applied by way of finder sequence switch contact 203 (3 to 5), for instance, of a finder circuit that has just found a calling line to move the sequence switch of finder ircuit F, for instance, out of its normal position 1 to cause it to take up the hunt for calling lines. I

Relay 17, which is energized in parallel with the relay 42, in operating closes a short circuit about finder sequence switch contact 229 (3 to 17), another short circuit about finder sequence switch contact 232 (8 to 17), and another short circuit about finder sequence switch contact 211 (2 to 16). As the relay 17 is held energized by way of the locking contact of relay 42 and finder sequence switch contact 203 (7 to 5), these short circuits are maintained from the moment that the selector switch commutator segment H is grounded in position 7 of the finder sequence switch until the finder sequence switch has moved through its cycle and out of position 5 in its repeated cycle of movement. The result of this is that while the finder sequence switch is repeating its cycle, current from the battery by way of resistance .coil 93 continues to flow to the test conductor 7 of the calling line by way of the test conductor of whichever branch of the finder circuit is in use for completing the connection. Consequently the calling line is guarded and prevented from being connected with by another hunting finder switch during the repetition of the cycle.

The relay 47 in operating also closes, at its inner upper front contact and armature, a branch to ground of the locking circuit for the relay 4?), which maintains that relay operated when the other branch of the locking circuit is open at finder sequence switch contact 209 (2 to 17 while the finder sequence switch is repeating its cycle. This holds the relay 43, and through it the relay 4:4, energized to continue the connection of the finder circuit with the set of brushes 7 O 71. 72 and 73 in case it is that set through which connection has been completed with the calling line.

What is claimed is:

1. The combination with a group of telephone lines, of an extension circuit therefor having a plurality of branches, atesting device associated with each branch and responsive to the calling condition of any line, means for bringing said branches successively into connection with each of the lines of said group, and means under the control of each testing device for effecting the connection of said extension circuit with a call ing line by way of the associated branch.

2. The combination with a group of lines, of an extension circuit therefor, a switch having contacts upon which said lines terminate and brushes with which said extension circuit is adapted to be connected, duplicate testing devices associated with said switch and responsive to the calling condition of any of said lin s, means for bringing said testing devices separately into operative relation with each of said lines, and means operated in the response of either of said testing devices for completing the connection of said extension circuit with a calling line.

8. The combination with a group of lines, of an extension circuit therefor, a plurality of testing devices associated with said extension circuit, means for bringing each of said testing devices successively under the control of each of the lines of said group, and means operated in the actuation of any of said testing devices for completing the connection of said extension circuit with the line to which the testing device has responded.

4. The combination with. a group of lines, of a common circuit therefor, said circuit having a plurality of branches each provided with a testing device responsive to an abnormal electrical condition of any of the lines of said group, means for bringing said branches successively into connection with each of the linesof said group, and means operated in the response of any of said testing devices to the abnormal electrical condition of a line with which it is temporarily in connection for establishing a permanent connection of the aforesaid common circuit with said line by way of the associated branch.

5. The combination with a group of lines, of means cont-rolled by any line in calling for changing the electrical condition thereof, a finder switch having contacts upon which said lines terminate, means for moving said switch, duplicate testing devices associated with said switch, said testing devices being responsive to the changed electrical condition of a tested line and being brought successively into connection with each of the lines of said group in the movement of said switch, and means actuated in the response of any of said testing devices for stopping said finder switch in engage ment with the terminals of the calling line.

6. The combination with a group of lines, and a common circuit therefor, of duplicate testing devices associated with said common circuit and responsive to the electrical dition of said lines, means for bringing duplicate testing devices successively connection with each of the lines of group, and means for completing the connection of said common circuit with a tested line upon the response of either of said testing devices.

7. The combinationwith a group of lines and a. common circuit therefor, of duplicate testing devices associated with said common circuit and responsive to the electrical condition of said lines, means for bringing said duplicate testing devices successively into connection with each of the lines of said group, and means for completing the connection oi said common circuit with a tested line and rendering said devices inoperative upon the response of either of said devices.

8. The combination with a group of lines and a common circuit therefor, of an automatic switch having contacts upon which said lines terminate and brushes to which said common circuit is connected, means for moving saidbrushes over s id contacts, dnplicate testing devices associated with said common circuit and brought successively into connection with each of said lines in the movement of said switch, said testing devices being responsive to an abnormal electrical condition of any of said lines,'and means actuated in the operation of either of said testing devices for stopping the switch, connecting the common circuitto the line to which the testing device has responded, and disconnecting the testing devices.

9. In a telephone system, a switch having a plurality of brushes and a series of contact terminals 00111111011 to said brushes, a group of telephone lines connected with said contact terminals, means for causing said brushes to move together over said series and simultaneously engage diilterent contact terminals thereof, and automatic means under the control of any of said lines :for stopping the movement of said brushes when any one of them engages the terminal of said line. 7

10. An. automatic switch having a plurality of contact terminals arranged in a single bank, a plurality of brushes arranged to simultaneously engage diilerent terminals and to successively engage. all. of the terminals of said bank, a common circuit for said brushes, and selecting means for completing said circuit through either one of said brushes and the contact terminals with which it is in engagement.

11. An automatic switch comprising a series of sets of contact terminals, a plurality of sets of brushes arranged simultaneously to en difierent sets of contact terminals and successively to engage all. of said of contact terminals of the series, and electromagnetic mechanism under the joint control of either set of brushes and the set of terminals with which it is in engagement for rendering that set of brushes electrically active and the other set electrically inactive.

1:2. An automatic switch having a series of contact te minals and a plurality of brushes each of which cooperates with all of said contact terminals, a circuit common to said brushes, and means under the joint control of any of said brushes and any of the contact terminals which it engages for exclusively including that brush and the associated contact terminal in said circuit.

13. The combination with a group of tele-- phone lines, of a finder circuit therefor having a plurality of branches, an automatic switch having a series of contact terminals with which the lines or said group are connected and a plurality of brushes with which said finder circuit branches are connected, each oil. said brushes being arranged to cooperate with all the contact terminals of said series, means for moving said plurality of brushes simultaneously into engagement with a corresponding plurality of said contact terminals, and selecting means for exclusively completing the connection of said finder circuit with a certain one of said brushes and the terminal with which it is in engagement. I

let. The combination with a group of multiple brush switches, each switch of the group having a single series of contact terminals a ranged to be engaged successively by each of the brushes of the corresponding switch, of a group of lines multipled to the contact terminals of said switches, a group of extension. circuit-s each having a iluralit of branches res ectivel connected with the brushes of the corresponding switch,

means forcausing thefbrushes of one. of

one of said l' res upon the engagement of one oi. the brushes of the rotating switch with the contact terminal of that line for stopping-the rotation of said switch, exclusively completing the minnection of said extension circuit with the brush that is in engagement with said line, and starting the rotation of: another of said switches.

15. The co1'1'1bii1iation with a group of lines, of an extension circuit therefor having a plurality of branches, means for closing said branches simultaneously to difi'erent lines and successively to all of the lines of said group, and meansfor opening all but one ot said branches.

16. The combination with a group of telephone lines, of an extension circuit therefor 'haringa plurality of branches, means actuated by any oi said lines 111 calllng for.

changing the electrical condition thereof, means for closing said branches simultaneously to different telephone lines and successively to all of the telephone lines of said group, andineans responsivc to the changed electrical condition of any line for opening all the branches of said extension circuit excepting the branch closed to the line.

The combination with a switch hav ing a plurality of contact terminals and plurality ot brushes, of *onp of telephone lines connected with saic contactterminals, an extension circuit having branches connected with said. brushes, means for moving said brushes together to bringeach successively into engagement wit-i all of the contactterminals oil? said. switch and both simultaneously into eng rement with dillercnt contact terminals, a. ping the lDO'fJGHlQll'L) oi said brushes.

18. The combination witha switch having a plurality oi? contact terminals anda plurality oi? brushes, of a group of tele 'ihone lines connected with said contact terminals, an extension circuit having branches connected with said brushes, means for moving brushestogetl'ier to bring each successively into engagementwith all of said contact terminals and both simultaneously into engagement with difi'eent contact terminals,'n1eans for stopping the movement of said brushes, and means for rendering in active all but one of the branches of said extension cir uit.

19. The combination with a group of telephone lines, of an extension circuit'therefor having a plurality of branches, means actuated by any of said lines in calling "for changing the electrical condition thereof, a

switch having a series of contacts upon d means for step 1 which the lines of said group terminate and a plurality of brushes upon which the branches of said extension circuit terminate, means for moving said brushes simultaneously into engagement 'ith the contact terminals of different lines of said group and each brush successively into engagement with the terminals of all of the lines of said group, testing mechanism associated with said extension circuit and responsive to the changed electrical condition of a calling line for stopping said switch when a brush engages a calling line terminal, and means controlled by said testing mechanism for rendering inactive all but the branch ter- 'minating on the brush that has engaged the terminal of a calling line.

80. The combination with a group of telephone lines, of an extension circuit therefor having a plurality of branches, a switch having contacts upon which the lines of said group terminate and a plurality of brushes with which said branches of the extension circuit are connected, means actu ated by any of said lines in calling for changing the electrical condition thereof, means for causing said brushes to move simultaneously into engagement with different contacts and each brush successively into engagement with all of the contacts of the switch, a testing device associated with each branch of the circuit responsive to the changed electrical condition of a calling line, and means controlled in the actuation of either of said testing devices for stopping the movement of said switch brushes and completing the connection of said extension circuit through the associated brushes and preventing its completion by way of another of said branches.

21. The combination with a group of telephone lines, of an extension circuit therefor having a plurality of branches, an electro magnetic switch associated with said extension circuit for alternatively completing the connection of said circuit th one or another of said branches, a finder switch hav ing a series of contacts upon which said telephone lines terminate and a plurality of brushes with which said branches are re spectively connected, means actuated by any line in calling for changing the electrical condition thereof, means for causing said brushes to move together to simultaneously engage different contacts and each successively to engage all of the contacts of said series, testing means associated with said branches during the movement of said brushes and responsive to the changed electrical condition of a calling line, and means actuated in the response of said testing means for stopping said switch brushes and controlling said electromagnetic switch to complete the connection of said extension circuit with the branch associated with the brush that has engaged the terminals of a calling line.

22. A selector switch having two series of contact terminals, means for moving said switch to test first one and then the other of said series, means actuated in the test of the first series for controlling the movement of the switch to test the secondseries, and means made operative by the failure to operate of said test actuated means for causing said switch to repeat the test of said first series.

23. A selector switch having a plurality of banks of contact terminals and a corresponding plurality of brushes, means for moving said switch, said movement being in two stages, means for selecting one of said brushes in the first stage of movement of said switch, means for causing the selected brush to select a contact terminal of the corresponding bank in the second stage of movement, and means for preventing the second stage of movement made operative by the failure to select a brush in the first stage of movement.

24-. A selector switch having a plurality of banks of contact terminals and a corre sponding plurality of brushes, means. for moving said switch, said movement being in two stages, means for selecting a particular brush in the first stage of movement of said switch, means for causing the selected brush to select a contact terminal of the corresponding bank in the second stage of movement, means actuated by the selection of a brush in the first stage of movement for causing the switch to proceed to its second stage, and means. actuated upon the failure to select a brush in the first stage of movement for causing the switch to repeat the first stage.

25. The combination with a calling line, of a plurality of operators positions. each position being provided with a plurality of connecting circuits, means for selecting an operators position and then selecting a connecting circuit of said position and extending said calling line thereto, and means made operative bv the failure of said selecting' means to select an operators position for causing said means to repeat its operator-selecting operation.

26 A selector switch having two stages of movement. operators positions adapted to be selected by said switch in its first stage of movement, connecting circuits adapted to be selected bv said switch in its second stage of movement. and means made operative by the failure of said switch to select an operators position for preventing the movement of said switch to its. second stage and for causing the switch to repeat its first or oporator-selecting stage.

27. The comb nation with a plurality of operators positions each provided with conthereof and eXtend said calling line thereto,

and means made operative by the unavailability of all of said operators positions for causing said switch to repeat its position selecting operation and preventing it from starting its connecting circuit selecting operation.

28. The combination with aplurality of operators positions each having a plurality of connecting circuits, of a selector switch, means for causing said switclrtoselect an available operators position in the first stage of its movement and to select an idle connecting circuit in the second stage, or its movement, and means controlled by theunavailability of all of said operators positions for causing said switch to repeat the first stage of its movement and preventing it from entering into the second stage of its movement. v

29. The combination with a plurality of operators positions each provided with a plurality of connecting circuits, of a callextending circuit, a selector switch having two stages of movement, means for selecting an operators position in the first stage of movement, means for selectinga connecting circuit of the selected position and extend ing said call-extending circuit thereto in the second stage of movement, means made operative by the selection 01": an operators position in the first stage torcausing said selector switch to proceed to the second stage of its movement, and means made operative by the passage of said selector switch through its first stage without selecting an operators position for causing said switch to repeat its operator-selecting stage of movement.

30. A selector switch having a brush and a series of contact terminals, means for causing said brush to move over and test said terminals, means actuated in the further movement of said switch for causing said brush to return and repeat its testing oper ation, a test circuit made operative by the engagement of said brush with a predetermined terminal, means actuated in the operation of said test circuit for rendering inoperative said bruslrreturning and retesting means, and a second series of contact ter minals tested by said switch in the continued movement thereof.

31. The combination with a selector switch, of means for causing the same in the initial stage of its movement to test torand select an available operators position, and in its further movement to test for and select an idle connecting circuit of that position, mechanism operating at theend of the initial movement to prevent the further movement ofthe switch and cause it to re peat its initial movement, and means made operative by theselection of an operators position in the initial movement of said switch for rendering inoperative the aforesaid mechanism. I

32. The combination with a plurality of circuits divided into groups, of a common test circuit associated with each group, a selector switcln'rneans for moving the same,

said switch being adapted to test the aforesaid test circuits in the initial stage of its movement and to test the circuits of a selected group in its further movement, controlling means made operative at the conclusion of the initial stage ofmovementot said switch for causing the switch to return and repeat its initial testing stage, and

means responsive to a test circuit in the ini-' tial stage of movement for rendering inoperative said controlling means.

38. The combination with a selector switch having a plurality of normally inactive brushes and a corresponding plurality oi groups of contact terminals, of means for moving said switch, means for selecting and rendering active one of said brushes in the first stage of 'movement of saidswitch,

its second stage and causing it to repeat its bri islrselecting movement.

- 34:. The combination with a group of telephone line? of a group of operators posi tions each provided with a plurality of connecting circuits, a finder circuit having two branches, means for establishingconnection between said finder circuit and any calling.

line of said group over either of said branches, means for selecting an operator s positionand then extending said, finder circuit to one of the connecting circuits thereof, and means made operative by the failure or said selecting means to select an operators position for causing the same to repeat its operator-selecting operation. 1

35. The combination with a group of tele phone lines, of aplurality of operators positions each provided with a pluraiity' of connecting switch for establishing connection between said finder circuit and any one of said telephone lines, a selector switch for selecting an available operztors positionv and c1; anding said finder circuit to an idle connecting circuit thereof, duplicate testing apparatus and circuits controlling the connection or" said finder circuit with a calling l ne of circuits, a finder circuit, a finder 

